How to Effectively Eliminate Black Sigatoka Disease on your Plantain Farm

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Have you ever been irritated at the sight of brown-yellowish streaks on your plantain leaves, discoloring the leaves and greatly reducing your yield-per-hectare?

I used to feel irritated too. Healthy, vigorously growing plantain trees would just suddenly be inflicted with small brown or yellowish spots and before long, they’ve developed into streaks which discoloured the fresh, green leaves of the plantain.

Identifying the Black Sigatoka Disease

The first symptoms of black Sigatoka disease are tiny, chlorotic spots that appear on the bottom (abaxial or underside) surface of the 3rd or 4th open leaf. The spots grow into thin brown streaks running parallel and limited by leaf veins.

These streaks aggregate and eventually form spots that coalesce, form a chlorotic halo, and eventually merge to cause extensive necrosis. The color of the streaks becomes darker, sometimes with a purple tinge, and visible on the top (adaxial) surface.

The lesions then enlarge, becoming fusiform or elliptical, and darken to give the characteristic black streaking of the leaves. Adjacent tissue often has a water-soaked appearance, especially under conditions of high humidity.

When the disease severity is high, large areas of the leaf may become blackened and water-soaked. On the necrotic tissue, numerous, tiny, black, globose fruiting bodies (pseudothecia) containing sac-like structures (asci) filled with ascospores will emerge from the underside of the leaf.

Factors That Favour Its Spread

The most likely route of infection is through the importation of infected plant materials onto the farm.

Black Sigatoka is seen to be more serious in the rainy than dry season. This is because the fungus requires water for producing and spreading the spores that infect other leaves or plants.

High humidity in the field also encourages rapid development of the disease. Conditions that encourage high humidity in the field include high plant density, poor field sanitation, high weed growth and poor drainage, in addition to heavy rainfall.

Damaging Effects of Black Sigatoka Disease

It causes rapid death of plantain leaves.

It destroys all leaf tissues.

It reduces the photosynthetic capability of the plant to manufacture food needed for growth and filling up of the bunch.

It also causes premature ripening.

Effectively Controlling the Disease

Use of Resistant varieties: This is the cheapest and most effective method of controlling plant diseases

Cultural management techniques: these are practices that reduce humidity in the field. These include maintenance of correct spacing or plant density, good field sanitation, better drainage of both water and air, better weed management, and removal of severely diseased leaves or portions of them from plants can also be used to obtain some measure of control.

Fertilization: of the plant also reduces the impact of leaf spot diseases through an increase in the rate of leaf production as a result of photosynthesis. The application of urea and other products onto infested plant debris on the ground can accelerate decomposition and thus reduce further the available spore inoculum.

De-leafing: removal of severely diseased or infected leaves and placing them on the ground can significantly reduce the efficacy of ascospore discharge.

Use of fungicides: this is very effective but very expensive to afford and also portends grave damage to the environment.

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Originally published at on February 7, 2017.